Make a montage of cropped data browser snapshots

crop_and_stitch.py

#!/usr/bin/env python                                                                                                                                                                        

import subprocess
import sys
from os import listdir
from os.path import isfile, join
import time

# image, crop dimensions                                                                                                                                                                     
img_dir = sys.argv[1]
left = sys.argv[2]
right = sys.argv[3]
top = sys.argv[4]
bottom = sys.argv[5]
img_out = sys.argv[6]

# get list of images in img_dir                                                                                                                                                              
imgs = [f for f in listdir(img_dir) if isfile(join(img_dir, f))]

for img_base in imgs:
    if 'cropped' in img_base: continue

    print(img_base)
    img = '{}/{}'.format(img_dir, img_base)

    # arrange the output file's name and path                                                                                                                                                
    img_base = img[:img.rfind(".")]
    extension = img[img.rfind("."):]
    path = img[:img.rfind("/")]
    img_cropped = img_base + ".cropped" + extension

    # get the current image size                                                                                                                                                             
    data = subprocess.check_output(["identify", img]).decode("utf-8").strip().replace(img, "")
    size = [int(n) for n in data.replace(img, "").split()[1].split("x")]

    # calculate the command to resize                                                                                                                                                        
    w = str(size[0] - int(left) - int(right))
    h = str(size[1] - int(top) - int(bottom))
    x = left
    y = top

    # execute the command                                                                                                                                                                    
    cmd = ["convert", img, "-crop", w+"x"+h+"+"+x+"+"+y, "+repage", img_cropped]
    subprocess.Popen(cmd)

time.sleep(1)

# horizontally stitch slices                                                                                                                                                                 
cmd = ["convert", "+append", '{}/*.cropped.png'.format(img_dir), img_out]
subprocess.Popen(cmd)

ImageMagick is required to run the identify and convert commands needed by the script.

This toolkit can be installed on a Mac via brew install ImageMagick (Homebrew) or the usual package managers for Linux.

To use this script, start with a folder of snapshots (e.g., /home/areynolds/snapshots):

$ python crop_and_stitch.py /home/areynolds/snapshots 400 400 0 0 /home/areynolds/montage.png

The values 400 400 0 0 here are arbitrary and depend on taste. These simply crop 400 pixels from the left and right sides of each snapshot. The top and bottom dimensions are left unchanged (0). Adjust these depending on how much you want each stripe to show.

The output is written to the file /home/areynolds/montage.png, which is one image made up of all the vertical stripes created from cropping.